Common UV blocker kills young coral, creates coral "zombies"

A chemical found in many soaps, laundry detergents, and cosmetics is killing young coral reefs at concentrations commonly found in the environment, according to a new study.

Corals, which provide habitat for a rich array of fish and other marine life, are threatened worldwide. The new study is the first to find that benzophenone-2 (BP-2) is toxic to coral reefs, although it builds upon previous studies that reported that corals are harmed by other chemicals in wastewater and runoff.

Researchers exposed baby corals in a laboratory to different concentrations of BP-2, which is found in hundreds of personal-care products. Increased BP-2 exposure caused increased rates of coral death, DNA damage, and bleaching, which is when corals turn white, are stressed, and more likely to die.

The levels of BP-2 used in the study—ranging from 24 parts per billion to 246 parts per million—are within what has been found in U.S. wastewater effluent.

Once in the environment, BP-2 can quickly “kill juvenile corals at very low concentrations—parts per billion,” the authors wrote.

Researcher worries about "zombies"

“What’s worrying is that if this chemical harms young coral, we won’t get coral recruitment around the world,” said Craig Downs, a researcher at Haereticus Environmental Laboratory in Virginia who led the study. “This will create coral zombies—coral where’s there’s adults but not recruited young, so the reef will eventually go away.”

The Caribbean alone has had roughly 80 percent of its corals disappear over the past 50 years from pollution, development, and climate change. Pesticides, petroleum compounds, and agricultural nutrients such as phosphorous and nitrogen also threaten coral-reef health.

“This is more bad news for coral reefs, more evidence of the pervasive and pressing impacts of land-based sources of pollution,” said Michael Risk, a professor at Canada’s McMaster University in a prepared statement. Risk was not involved in the study.

“The results show that something humans use to protect their skin or toiletries can reach the sea from wastewater discharges and shut down coral reproduction,” he said.

Study head warns of economic impact 

Downs warned of the economic impact. The roughly 1,200 square miles of coral reefs in the United States generate more than a billion dollars per year due to coastal protection, fisheries, tourism, recreation, and biodiversity promotion, according to a 2003 study. The impact is even greater for regions with more reefs area, such as Southeast Asia, which benefits annually from corals to the tune of about $12.5 billion.

BP-2 also has been linked to cancer and thyroid disruption in people.

The chemical is used to protect bath salts, body fragrances, lotions, shampoos, soaps and laundry detergents from ultraviolet light, which make products lose their colour. It is similar to oxybenzone, the active ingredient in many sunscreens, although it is not used in U.S. sunscreens.

Often found in wastewater, it is considered an emerging contaminant of concern by the U.S. Environmental Protection Agency.